Packet-based communication systems allow a user of a device, such as a personal computer, to communicate across a computer network such as the Internet. Packet-based communication systems include voice over internet protocol (“VoIP”) communication systems which can support calls, and other communication sessions, between users of the communication systems. These communication systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long-distance communication. To use a VoIP system, client software must be installed and executed on the device. The client software provides the VoIP connections as well as other functions such as registration and authentication. A user of a packet-based communication system can establish calls with other users who are simultaneously logged in to the communication system.
Client software for VoIP communications can be provided by an application at a device, for example, client software may be provided in the form of a plug-in program which can be executed within a host application, such as a web browser at a device. The plug-in program can handle VoIP calls and use the host application for displaying a call control interface thereby allowing a user to set up and control VoIP calls through the host application. The use of such a plug-in program in a web browser (or other host application) facilitates the set up, and control, of VoIP calls for a user who is using the web browser. The use of a plug-in program is a particularly user friendly method for implementing the client software at the device.